Cephalexin (Keflex)
Cephalexin in Brief
- Active ingredient: cephalexin
- Common brand names: Keflex, Keftabs, Biocef
- Drug class: first-generation cephalosporin antibiotic
- FDA Approved: January 4, 1971
- Chemical Formula: C16H17N3O4S
FDA approved uses
- Respiratory tract infections caused by Streptococcus pneumoniae
and Streptococcus pyogenes
- Otitis media due to Streptococcus pneumoniae, Haemophilus influenzae,
Staphylococcusaureus, Streptococcus pyogenes, and Moraxella catarrhalis
- Skin and skin structure infections caused by Staphylococcusaureus
and/or Streptococcus pyogenes
- Bone infections caused by Staphylococcusaureus and/or Proteus mirabilis
- Genitourinary tract infections, including acute prostatitis, caused
by Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae
Cephalexin "pros" and "cons"
Advantages:
- excellent safety record
- very low incidence of allergic reactions
- may be taken without regard to food
- superior to penicillin in the streptococcal throat infection 2.
- active against most gram-positive bacteria.
Disadvantages:
- short half-life requires QID dosing: the serum half-life is 0.5–1.2 hours in adults, about 5 hours in neonates and 2.5 hours in children 3–12 months of age.
- less active than cefatrizine and cefaclor against Escherichia
coli, Klebsiella pneumoniae and Proteus mirabilis 2.
Mode of action
Cephalexin inhibits the third and last stage of bacterial cell wall synthesis by preferably binding to specific proteins (PBPs) that are located inside the bacterial cell wall.
Time for Cephalexin to clear out the system
Cephalexin mean half-life is 50 to 80 min. It may take 4 to 5 hours
to clear out of the system.
Further reading
References
- 1. Disney FA, Dillon H, Blumer JL, Dudding BA, McLinn SE, Nelson
DB, Selbst SM. Cephalexin and penicillin in the treatment of group
A beta-hemolytic streptococcal throat infections. Am J Dis Child. 1992 Nov;146(11):1324-7.
- 2. Luh KT, Chao HP, Ho SW, Hsieh WC. Comparison of in vitro antibacterial
activity of four oral cephems: cephalexin, cefaclor, cefatrizine and
cefadroxil. Zhonghua Min Guo Wei Sheng Wu Ji Mian Yi Xue Za Zhi. 1984
Feb;17(1):11-8. PubMed
Published: March 31, 2008
Last updated: April 25, 2011
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